1. Field of the Invention
The present invention relates to a regenerative heat pump.
2. Description of the Prior Art
A regenerative heat pump typically produces an output power required for heating or cooling a certain space by compressing or expanding a gas such as helium which is filled in a cylinder.
Generally, the interior of the cylinder of such a regenerative heat pump is divided into three chambers, that is, a high temperature chamber, a medium temperature chamber and a low temperature chamber by way of two displacers. A gas filled in the high temperature chamber is directly heated by means of an external heating means.
The displacers reciprocate in the cylinder by the expansion of the gas heated and, also, by the rotation of a crank which is connected to each rod of the displacers. The crank is rotated by means of a motor.
The gas is fed into the three chambers by the displacers displaced due to the expansion of the gas as well as the rotation of the crank. The temperatue of the gas contained in the respective chambers rises up to a level of a steady state and is maintained at a constant temperature level. At this time, the displacers are continuously moved.
For the chambers of the cylinder, the compression and expansion of the gas is repeated so that the heat pump produces a work, that is, a heating or cooling work according to the compression or expansion of the gas.
FIG. 1 shows such a conventional regenrative heat pump. As seen from the drawing, the heat pump includes a cylinder 31 of which the interior is divided into three spaces, that is, a high temperature chamber 38, a medium temperature chamber 39 and a low temperature chamber 40 by high and a low temperature displacers 32 and 33. These chambers are different in temperature. The high temperature displacer 32 is connected through a first connecting rod 34 to a crank member and the low diplacer 33 is also connected to the crank member 43 through a second connecting rod 35. The first and second connecting rods 34 and 35 are connected to the crank member 43 in a phase difference relation of 90 degrees.
A heat tube 36 is formed integrately with a head 49 of the cylinder 31 and is communicated to the high temperature chamber 38. The heat tube 36 is directly heated by means of an external heating means or heater 37 and executes a direct heat transfer to the gas contained in the high temperature chamber 38. When the heating means 37 begins to heat the tube 36, the crank member 43 is moved by a motor (not shown) and the displacers 32 and 33 reciprocate in the cylinder 31 in accordance with the heating expansion of the gas and the rotation of the crank member 43.
Multiple O-rings are disposed on an external periphery surface of the displacers 32 and 34 to prevent a leak of the gas from the respective chambers. The gas is fed to the high temperature chamber 38, the medium temperature chamber 39 and the low temperature chamber 40 through a flow path 45 which is arranged at an external periphery of the cylinder 31 and extended into the respective chambers 38, 39 and 40.
In addition, a high temperature regenerator 41 is disposed at a predetermined position of the flow path defined between the high temperature chamber 38 and the medium temperature chamber 39. A low temperature regenerator 42 is disposed at a predetermined position of the flow path between the medium temperature chamber 39 and the low temperature chamber 40. These high and low temperature regenerators 41 and 42 absorb or radiate heat from the gas to control the temperature of the respective chambers 38, 39 and 40 constantly.
As mentioned above, a variation of pressure in a closed system occurs due to the displacement of the displacers 32 and 33 located in the cylinder 31 and the repeated compression and expansion of the gas is carried out in the system to produce the heating or cooling work.
With such a conventional regenerative heat pump, each volume of the high, medium and low temperature chambers 38, 39 and 40 defined by the displacers 32 and 33 is varied according to the displacement of the displacers 32 and 33 while the total volume of the chambers 38, 39 and 40, that is, of the cylinder 31 remains constant.
Further, such a heat pump cannot produce a work w expressed by the following equation 1 for obtaining the heating or cooling work. EQU W= PdV.sub.T =P(V.sub.T2 -V.sub.T1) (1)
where, dV.sub.T is defined by d (V.sub.H +V.sub.M +V.sub.L); P denotes a total pressure, V.sub.T is the total volume of chambers 38, 39, 40,
V.sub.H is the volume of the high temperature chamber, PA1 V.sub.M is the volume of the medium temperature chamber, PA1 V.sub.L is the volume of the low temperature chamber.
Referring to FIG. 2a, it is undertood that even if the volumes of the respective chambers 38, 39 and 40 are varied as shown in the drawing, the total volume, that is, the volume of a rectangular region defined by the sum V.sub.T (=V.sub.H +V.sub.M +V.sub.L) is unchanged, and the pressure is varied while the volume is unchanged as shown in FIGS. 2b and 2c.
Accordingly, in such a conventional regenerative heat pump, the total volume V.sub.T of the chambers can be obtained by a relation of V.sub.T2 =V.sub.T1. Therefore, in the above equation 1, W equals zero, so even if the total pressure of the system is varied, a work for heating or cooling output is not assurred because the total volume V.sub.T is unchanged. Therefore, the displacers 32 and 33 cannot themselves produce a driving force.
For this reason, the motor must be continuously operated so as to continue the operation of the displacers 32 and 33. As a result, power consumption is greatly increased and where the motor is operated for a long time, a heat generated undesirably affects the motor, resulting in a reduction of the life time of the motor and thus requiring an additional means for cooling the motor.